HVAC sizing

[PowerdT]

Can anyone please verify if I sized Air Condition correctly. Thank you in advance.

The system is 480V, 3p,60Hz

MCA is given 22.6A​

MOP is given 25A​

FLA is given 24​

LRA is given 130

1. Branch circuit per NEC 310.15—> (3) #12AWG at 75 degree.
2. OCPD is given maximum 25A HACR type circuit breaker by the manufacture
3. Disconnect per 440.12A1—>1.15x 18.08 = 20.47—> next standard 30A, 3 pole Non-disconnect switch
4. EGC per 250.122–> (1) #10AWG

 

[texie]

1) OK if not using NM cable and the equipment is rated for 75 degree (likely)
2) 25 amp is correct and a standard value
3) Good
4) EGC never has to be larger than the phase conductors.

 

[ActionDave]

Pretty close. 1 through 3 are correct. Number 4 is incorrect. 250.1??, a wire type equipment ground is not required to be larger than the circuit conductors.

 

[PowerdT]

1) OK if not using NM cable and the equipment is rated for 75 degree (likely)
2) 25 amp is correct and a standard value
3) Good
4) EGC never has to be larger than the phase conductors.

What changes if NM cable is used ?

 

[PowerdT]

Pretty close. 1 through 3 are correct. Number 4 is incorrect. 250.1??, a wire type equipment ground is not required to be larger than the circuit conductors.

So EGC will be #12AWG?

 

[augie47]

What changes if NM cable is used ?

NM is requred to use it's 60° ampacity of 20 amps

 

[texie]

So EGC will be #12AWG?

Yes.

 

[david luchini]

How is FLA larger than MCA?

 

[PowerdT]

How is FLA larger than MCA?

Actually the FLA and the LRA are listed under the minimum disconnect Rating

 

[LarryFine]

Agree with above responses.

How is FLA larger than MCA?

Manufacturer's issue; still within 25a conductor rating.

 

[don_resqcapt19]

The FLA being higher than the MCA does not comply with either the listing standard or the NEC rules. The manufacture needs to send out the correct tag.

 

[ActionDave]

What changes if NM cable is used ?

In the real world nothing changes, it's just a ticky tack code requirement with no evidence to back it up.

 

[PowerdT]

I have attached the picture of the data, the highlighted one

 

[PowerdT]

The FLA being higher than the MCA does not comply with either the listing standard or the NEC rules. The manufacture needs to send out the correct tag.

the FLA is listed under the min disconnect. Please check the attached data sheet. Maybe it is listed to size the disconnect?

 

[Mgraw]

the FLA is listed under the min disconnect. Please check the attached data sheet. Maybe it is listed to size the disconnect?

What do the notes say?

 

[david luchini]

the FLA is listed under the min disconnect. Please check the attached data sheet. Maybe it is listed to size the disconnect?

I think you are correct. It's not actually the full load amps of the unit, but 115% of the sum of all currents for Disconnect Ampere Rating per 430.110(C)(2).

 

[PowerdT]

What do the notes say?

The notes say:

1. Minimum circuit Ampacity
2. Dual element. Time delay type
3. HACR Type per NEC
4. Non-fused Disconnect, verify on the unit nameplate that the disconnect is properly sized for the application. Units with field installed electric heat kits may exceed the factory installed disconnect amperage rating

 

[texie]

The notes say:

1. Minimum circuit Ampacity
2. Dual element. Time delay type
3. HACR Type per NEC
4. Non-fused Disconnect, verify on the unit nameplate that the disconnect is properly sized for the application. Units with field installed electric heat kits may exceed the factory installed disconnect amperage rating

3) Just as an FYI all breakers today are rated HACR as part of their listing. Years ago you had to specify the HACR rating.